CA1117601A - Locked-oscillator repeater with modulation frequency feedback - Google Patents
Locked-oscillator repeater with modulation frequency feedbackInfo
- Publication number
- CA1117601A CA1117601A CA000329508A CA329508A CA1117601A CA 1117601 A CA1117601 A CA 1117601A CA 000329508 A CA000329508 A CA 000329508A CA 329508 A CA329508 A CA 329508A CA 1117601 A CA1117601 A CA 1117601A
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- oscillator
- signal
- output
- repeater
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/155—Ground-based stations
- H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Radio Relay Systems (AREA)
- Transceivers (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In accordance with this invention, a radio repeater of the injection locked oscillator type is provided with a feedback circuit for changing the free-running or rest frequency of the locked oscillator so that it follows the frequency deviations of the frequency modulation signal being repeated. This results in a higher gain for the repeater.
In accordance with this invention, a radio repeater of the injection locked oscillator type is provided with a feedback circuit for changing the free-running or rest frequency of the locked oscillator so that it follows the frequency deviations of the frequency modulation signal being repeated. This results in a higher gain for the repeater.
Description
The operating capabilities of short range communication radio sets can be materially improved by use of repeaters. The effective range of radio sets is often reduced by natural obstacles such as dense foliage or hilly terrain. A strategically placed repeater may be used to overcome these natural obstacles by providing a transmission path free of obstructions, thereby extending the effective range of the radio set and improving its tactical value.
For example, troops often set up radio sets in valleys or behind hills for protection and a hilltop repeater in such a situation can greatly expand the capability of such tactical radio sets.
Typically, repeaters operate either by receiving and retransmitting at the same frequency~ repeaters of this type being known as Fl-Fl repeaters~
or by receiving at one frequency and, retransmitting at a second frequency, repeaters of this type being known as Fl-F2 repeaters.
Fl-Fl repeaters are more desirable in many applications since they utilize less hardware and require a smaller portion of the frequency spectrum.
However, in these repeaters some means must be provided to prevent coupling between the transmitter and receiver,which can cause oscillation or singing.
The present invention is a repeater in which signal amplification is achieved by means of an injection locked oscillator. The incoming signal, which may be too noisy for direct ampliiication, is applied to an oscillator with a free-running frequency substantially equal to the center or carrier frequency of the incoming frequency modulated signal. The oscillator locks onto the injected signal and follows the modulation thereon. The oscillator output is then amplified and transmitted. The figure of merit of such an injection locked oscillator is the locking ~ain, defined 2S the ratio of power sutput to power input. The locking gain is inversely proportional to the difference between the free-running or center frequency of the oscillator, and the instantaneous injection frequencyO Thus, as the deviation of the received injected signal increases, the locking gain decreases. ~he present invention involves a means for permitting the free-running or center frequency of the oscillator to follow or track the frequency deviations of the injected `'"' ~
s;glal, s) tlat tl(~ 1~; u;l~ y d u~i at i l!l`l i '~ I ( d~l( ('d Ul[l II(`n( (`
tlt l.oclirlg g~ bili ~d a~ e(l.
T'ilis ill;~ lt ;(~ )r(.)vid~ rn~ r-ec-rullning frequtncy oi an inicction loclci~cl o~lcilla~:o- ~;o tll,lt iL lollows the impressed mo bll.3tion. lhis :i~s done by rm~ s or a re((ll)a l ~sL(~m wll~reby a sample of tle osci.llat)r output i.s a~plie(i to ;:l l~r~ llellcy ]i;cr;~ninaL)r which recovers the modllati(lll of signal being retrallsmitt l~ Tllis modulation is applied to a voltage controlled reactance in Lhe osc:;]laL(n- tanlc ci.rcuit in such a manner as to pul l the free-runni.ng osci~ Lol- Ir~(l(lcncy L:<)ward the instantaneous Erecluerlcy thet-eo(, By thus decreasirg, Lll( cl:ir(erence between the free-running alll instaltaneous oscillator rr (luellcv~ th( gain i.s increa.qed and stabili~.ed as exl)la;lled above.
I~RlEF DESCRIPTIONi ~J~` Tlll~` I)RAWlN(:
The sole f:igllre of the drawing is a block liai;laill of al~ ll radio repeater wllicll in orporlt~s an illustrative elllbo(lilll:llL ol l.lle present. ;.nvention~
In the drawing the antenna 11 serves for bol:il receiving an(l trans-mitting, The receiving channel comprises tl-le blocliY on llle rigllt sile Or the drawing and the tlallsn:i.tting channel those on ~ lel L. '1`11(` llybrid Isolator 13 and its associ.ated Automatic Impedcinc ~paLc~ g (,ircuit 14 serve to prevent the transmitted signal applied to tle antenna 11 via hybrid port 13a from entering the rec ivi.ng channel connected t) hv~l-;.d port 13c, and also directs the received signal from antenna ll to the rec(ivilg chanlel.. The operation of this automa~;.c impedance matcllilg al-7clllg~ (llL allcl thc hybrid isolator is e~plained in (letail in U.S. Patent 4,('28,64r al(l per se rorms nO
part of the present inv(ntion~
.: The receivecl si.gnal, after passing thr(:)uill l)i.r :t;ollal Coupler 1.5 is appli.ed to tunable Rl Amplifier 17 which is gani,-tulle(:l Wi.tll RF Power Amplifier 39 in the t.r ulsmitter chanrlel and also with l,o(a] ()sc;llat)r 18, as indicated by the dashed line 16 connecting these Ll~ cir uit elenents, Th~ aml)lifiel receivel sigllal is apl)li l to Receiv r ~li\(~r 1.(' t(get.ller with the oUti'JUt 07' the Local ()sc;.l.l.at)r which ]iLrers Froll t:b~ tuning of boti( RF
~'il~/
a~
stages by the inteImediate freq~ency. The IF Amplifier 21 selects the inter-mediate frequency from the mixer output and applies it to input port 23a of Hybrid Circuit 23. The Injection Locked Oscillator 25 is connected to port 23b of Hybrid 23. A voltage controlled reactance which may be a Varactor Diode 27, comprises part of the tank circuit of Oscillator 25. The output of the oscillator emerges from port 23c of Hybrid 23 and is applied to IF Amplifier 33 of the transmitter channel with a small portion thereof applied to Limiter-Discriminator 31. The Logarithmic Audio Amplifier 29 receives the discrimina-tor output. The log amplifier output is applied to Varactor 27 to control the capacitance thereof. After passing through Phase Shifter 35 the trans-mitted signal is heterodyned up in frequency in Mixer 37 to equal that of the received frequency. Tunable RF Power Amplifier 39 then further amplifies the signal before it is applied to the antenna 11 The function of Hybrid Circuit 23 is to isolate the receiving and transmitting channels by applying the output of the receiver IF Amplifier 21 to Oscillator 25 while directing most of the oscillator output to the trans-mitter channel. This may be accomplished for example if the port 23a of hybrid 23 is the anti-symetric port thereof, with port 23c being the symetric port and the oscillator port 23b being one of the hybrid collinear ports.
This arrangement would anticipate the use of a standard four port hybrid, that is, a magic tee. The fourth port, that i9 the hybrid collinear - port not coupled to the oscillator, would be terminated in a load in this instance and is not shown in the figure. It would also be desirable to insert a 3 db. or 10 db. pad between IF ampliiier 21 and Hybrid Circuit 23 to reduce any signals feeding back into the IF amplifier in this configuration.
A more desirable configuration would utilize a standard three port circulator as shown in the figure. This device provides the characteristics described above, specifically, isolation of the receiving and transmitting channels by applying the output of the receiver IF amplifier 21 to oscillator 25 while directing most of the oscillator output to the transmitting channel~
Mer-rimac Industries Inc. of West Caldwell, New Jersey fabricates several -u(N~(ir(lllators ~or IF fre(l~len~ies ill or(l~r Or 50 to lOOO MH~, such devices being well within the state of the art.
The ]imiter~discriminator is a conventional circuit element found in most frequency modulation receivers. The limiter removes any arnplitude modulation on the signal and thus puts out a constant-amplitude signal. The discriminator has a center-frequency equal to the free-running frequency of Oscillator 25, this being its frequency in the absence of an input signal.
The discriminator output is the frequency modulation on the signal being repeated. This modulation is amplified in Logarithmic Audio Amplifier 29 and then applied to Varactor 27, which is arranged to pull or modulate the free-running oscillator frequency so that it tends to follow the instantaneous frequency deviations caused by the injected signal frequency. As stated above, this arrangement results in higher repeater gain than would be otherwise attainable. The feedback loop comprising the Hybrid Circuit 23, Limiter-Discriminator 31, Log Amplifier 29 and Varactor 27 must be designed with substantially zero phase delay or shift in order to achieve the desired result. Since the varactor capacitance varies approximately inversely with the voltage applied thereto and since the oscillator fre-quency varies inversely with the square root of capacitance, it is necessary to distort the discriminator output in a logarithmic fashion in order for the oscillator frequency to track or follow the detected frequency modula~
tion at the discriminator output. The required distortion or shaping is produced by the logarithmic amplifier.
While the invention has been illustrated in connection with an Fl-Fl repeater, it is applicable to any type of injection locked oscillator type of repeater. Accordingly, the invention should be limited only by the scope of the appended claimsO
:.,
For example, troops often set up radio sets in valleys or behind hills for protection and a hilltop repeater in such a situation can greatly expand the capability of such tactical radio sets.
Typically, repeaters operate either by receiving and retransmitting at the same frequency~ repeaters of this type being known as Fl-Fl repeaters~
or by receiving at one frequency and, retransmitting at a second frequency, repeaters of this type being known as Fl-F2 repeaters.
Fl-Fl repeaters are more desirable in many applications since they utilize less hardware and require a smaller portion of the frequency spectrum.
However, in these repeaters some means must be provided to prevent coupling between the transmitter and receiver,which can cause oscillation or singing.
The present invention is a repeater in which signal amplification is achieved by means of an injection locked oscillator. The incoming signal, which may be too noisy for direct ampliiication, is applied to an oscillator with a free-running frequency substantially equal to the center or carrier frequency of the incoming frequency modulated signal. The oscillator locks onto the injected signal and follows the modulation thereon. The oscillator output is then amplified and transmitted. The figure of merit of such an injection locked oscillator is the locking ~ain, defined 2S the ratio of power sutput to power input. The locking gain is inversely proportional to the difference between the free-running or center frequency of the oscillator, and the instantaneous injection frequencyO Thus, as the deviation of the received injected signal increases, the locking gain decreases. ~he present invention involves a means for permitting the free-running or center frequency of the oscillator to follow or track the frequency deviations of the injected `'"' ~
s;glal, s) tlat tl(~ 1~; u;l~ y d u~i at i l!l`l i '~ I ( d~l( ('d Ul[l II(`n( (`
tlt l.oclirlg g~ bili ~d a~ e(l.
T'ilis ill;~ lt ;(~ )r(.)vid~ rn~ r-ec-rullning frequtncy oi an inicction loclci~cl o~lcilla~:o- ~;o tll,lt iL lollows the impressed mo bll.3tion. lhis :i~s done by rm~ s or a re((ll)a l ~sL(~m wll~reby a sample of tle osci.llat)r output i.s a~plie(i to ;:l l~r~ llellcy ]i;cr;~ninaL)r which recovers the modllati(lll of signal being retrallsmitt l~ Tllis modulation is applied to a voltage controlled reactance in Lhe osc:;]laL(n- tanlc ci.rcuit in such a manner as to pul l the free-runni.ng osci~ Lol- Ir~(l(lcncy L:<)ward the instantaneous Erecluerlcy thet-eo(, By thus decreasirg, Lll( cl:ir(erence between the free-running alll instaltaneous oscillator rr (luellcv~ th( gain i.s increa.qed and stabili~.ed as exl)la;lled above.
I~RlEF DESCRIPTIONi ~J~` Tlll~` I)RAWlN(:
The sole f:igllre of the drawing is a block liai;laill of al~ ll radio repeater wllicll in orporlt~s an illustrative elllbo(lilll:llL ol l.lle present. ;.nvention~
In the drawing the antenna 11 serves for bol:il receiving an(l trans-mitting, The receiving channel comprises tl-le blocliY on llle rigllt sile Or the drawing and the tlallsn:i.tting channel those on ~ lel L. '1`11(` llybrid Isolator 13 and its associ.ated Automatic Impedcinc ~paLc~ g (,ircuit 14 serve to prevent the transmitted signal applied to tle antenna 11 via hybrid port 13a from entering the rec ivi.ng channel connected t) hv~l-;.d port 13c, and also directs the received signal from antenna ll to the rec(ivilg chanlel.. The operation of this automa~;.c impedance matcllilg al-7clllg~ (llL allcl thc hybrid isolator is e~plained in (letail in U.S. Patent 4,('28,64r al(l per se rorms nO
part of the present inv(ntion~
.: The receivecl si.gnal, after passing thr(:)uill l)i.r :t;ollal Coupler 1.5 is appli.ed to tunable Rl Amplifier 17 which is gani,-tulle(:l Wi.tll RF Power Amplifier 39 in the t.r ulsmitter chanrlel and also with l,o(a] ()sc;llat)r 18, as indicated by the dashed line 16 connecting these Ll~ cir uit elenents, Th~ aml)lifiel receivel sigllal is apl)li l to Receiv r ~li\(~r 1.(' t(get.ller with the oUti'JUt 07' the Local ()sc;.l.l.at)r which ]iLrers Froll t:b~ tuning of boti( RF
~'il~/
a~
stages by the inteImediate freq~ency. The IF Amplifier 21 selects the inter-mediate frequency from the mixer output and applies it to input port 23a of Hybrid Circuit 23. The Injection Locked Oscillator 25 is connected to port 23b of Hybrid 23. A voltage controlled reactance which may be a Varactor Diode 27, comprises part of the tank circuit of Oscillator 25. The output of the oscillator emerges from port 23c of Hybrid 23 and is applied to IF Amplifier 33 of the transmitter channel with a small portion thereof applied to Limiter-Discriminator 31. The Logarithmic Audio Amplifier 29 receives the discrimina-tor output. The log amplifier output is applied to Varactor 27 to control the capacitance thereof. After passing through Phase Shifter 35 the trans-mitted signal is heterodyned up in frequency in Mixer 37 to equal that of the received frequency. Tunable RF Power Amplifier 39 then further amplifies the signal before it is applied to the antenna 11 The function of Hybrid Circuit 23 is to isolate the receiving and transmitting channels by applying the output of the receiver IF Amplifier 21 to Oscillator 25 while directing most of the oscillator output to the trans-mitter channel. This may be accomplished for example if the port 23a of hybrid 23 is the anti-symetric port thereof, with port 23c being the symetric port and the oscillator port 23b being one of the hybrid collinear ports.
This arrangement would anticipate the use of a standard four port hybrid, that is, a magic tee. The fourth port, that i9 the hybrid collinear - port not coupled to the oscillator, would be terminated in a load in this instance and is not shown in the figure. It would also be desirable to insert a 3 db. or 10 db. pad between IF ampliiier 21 and Hybrid Circuit 23 to reduce any signals feeding back into the IF amplifier in this configuration.
A more desirable configuration would utilize a standard three port circulator as shown in the figure. This device provides the characteristics described above, specifically, isolation of the receiving and transmitting channels by applying the output of the receiver IF amplifier 21 to oscillator 25 while directing most of the oscillator output to the transmitting channel~
Mer-rimac Industries Inc. of West Caldwell, New Jersey fabricates several -u(N~(ir(lllators ~or IF fre(l~len~ies ill or(l~r Or 50 to lOOO MH~, such devices being well within the state of the art.
The ]imiter~discriminator is a conventional circuit element found in most frequency modulation receivers. The limiter removes any arnplitude modulation on the signal and thus puts out a constant-amplitude signal. The discriminator has a center-frequency equal to the free-running frequency of Oscillator 25, this being its frequency in the absence of an input signal.
The discriminator output is the frequency modulation on the signal being repeated. This modulation is amplified in Logarithmic Audio Amplifier 29 and then applied to Varactor 27, which is arranged to pull or modulate the free-running oscillator frequency so that it tends to follow the instantaneous frequency deviations caused by the injected signal frequency. As stated above, this arrangement results in higher repeater gain than would be otherwise attainable. The feedback loop comprising the Hybrid Circuit 23, Limiter-Discriminator 31, Log Amplifier 29 and Varactor 27 must be designed with substantially zero phase delay or shift in order to achieve the desired result. Since the varactor capacitance varies approximately inversely with the voltage applied thereto and since the oscillator fre-quency varies inversely with the square root of capacitance, it is necessary to distort the discriminator output in a logarithmic fashion in order for the oscillator frequency to track or follow the detected frequency modula~
tion at the discriminator output. The required distortion or shaping is produced by the logarithmic amplifier.
While the invention has been illustrated in connection with an Fl-Fl repeater, it is applicable to any type of injection locked oscillator type of repeater. Accordingly, the invention should be limited only by the scope of the appended claimsO
:.,
Claims (6)
CLAIMED ARE DEFINED AS FOLLOWS:
1. A radio frequency repeater comprising receiving means for receiving an incoming signal;
frequency reduction means, electrically in series with said receiving means, for reducing the frequency of a received incoming signal;
a free running injection locked oscillator into which said reduced frequency incoming signal is injected, said oscillator producing an output signal and having a tank circuit containing a voltage controlled reactance which determines the frequency of said injection locked oscillator;
sampling means, electrically coupled to the said injection locked oscillator, for sampling the output signal of said oscillator;
processor means, electrically coupled to said sampling means, for converting the sampled oscillator output to a control voltage, the magnitude of said control voltage being dependent upon the frequency of the sampled oscillator output, and applying said control voltage to the voltage con-trolled reactance in the tank circuit of the injection locked oscillator thereby causing the free running frequency of said oscillator to follow the frequency of the incoming signal;
frequency increasing means, electrically coupled to the output of said injection locked oscillator, for increasing the frequency of the injection locked oscillator output to a desired transmission frequency;
transmitting means, electrically coupled to the output of said frequency increasing means, for transmitting an outgoing signal; and isolation and coupling means for coupling the reduced frequency incoming signal to the injection locked oscillator and for coupling the out-put signal from the injection locked oscillator to the processor means and frequency increasing means.
frequency reduction means, electrically in series with said receiving means, for reducing the frequency of a received incoming signal;
a free running injection locked oscillator into which said reduced frequency incoming signal is injected, said oscillator producing an output signal and having a tank circuit containing a voltage controlled reactance which determines the frequency of said injection locked oscillator;
sampling means, electrically coupled to the said injection locked oscillator, for sampling the output signal of said oscillator;
processor means, electrically coupled to said sampling means, for converting the sampled oscillator output to a control voltage, the magnitude of said control voltage being dependent upon the frequency of the sampled oscillator output, and applying said control voltage to the voltage con-trolled reactance in the tank circuit of the injection locked oscillator thereby causing the free running frequency of said oscillator to follow the frequency of the incoming signal;
frequency increasing means, electrically coupled to the output of said injection locked oscillator, for increasing the frequency of the injection locked oscillator output to a desired transmission frequency;
transmitting means, electrically coupled to the output of said frequency increasing means, for transmitting an outgoing signal; and isolation and coupling means for coupling the reduced frequency incoming signal to the injection locked oscillator and for coupling the out-put signal from the injection locked oscillator to the processor means and frequency increasing means.
2. The radio frequency repeater of claim 1 wherein said voltage con-trolled reactance comprises a varactor diode.
3. The radio frequency repeater of claim 1 wherein said processor means includes a log audio amplifier and a varactor diode.
4. The radio frequency repeater of claim 1 wherein said isolation and coupling means comprises a three port circulator.
5. The radio frequency repeater of claim 1 wherein a plurality of amplifier means are included for amplifying the received incoming signal, the reduced frequency incoming signal, the oscillator output signal and the out-going signal.
6. The radio frequency repeater of claim 5 including phase shifting means in electrical series with the output of the amplifier means which amplifies the oscillator output signal.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US937,295 | 1978-08-28 | ||
| US05/937,295 US4218772A (en) | 1978-08-28 | 1978-08-28 | Locked-oscillator repeater with modulation frequency feedback |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117601A true CA1117601A (en) | 1982-02-02 |
Family
ID=25469737
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000329508A Expired CA1117601A (en) | 1978-08-28 | 1979-06-11 | Locked-oscillator repeater with modulation frequency feedback |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US4218772A (en) |
| CA (1) | CA1117601A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4849963A (en) * | 1985-10-15 | 1989-07-18 | Minori Kawano | Cellular radio telephone enhancement circuit |
| US4862514A (en) * | 1986-11-24 | 1989-08-29 | World Electronics, Inc. | Hybrid electronic radio repeater |
| US6212397B1 (en) * | 1996-12-23 | 2001-04-03 | Texas Instruments Incorporated | Method and system for controlling remote multipoint stations |
| KR100546556B1 (en) * | 1997-12-27 | 2006-04-21 | 엘지전자 주식회사 | Portable terminal by code division multiple access |
| US6529712B1 (en) * | 1999-08-25 | 2003-03-04 | Conexant Systems, Inc. | System and method for amplifying a cellular radio signal |
| US6864755B2 (en) | 2000-10-06 | 2005-03-08 | Alfred E. Mann Institute For Biomedical Engineering At The University Of Southern California | Switched reactance modulated E-class oscillator design |
| US7005935B2 (en) * | 2001-10-05 | 2006-02-28 | Alfred E. Mann Institute For Biomedical Engineering At The University Of Southern California | Switched reactance modulated E-class oscillator |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3566234A (en) * | 1968-11-07 | 1971-02-23 | Cutler Hammer Inc | Concurrent same-frequency fm radio repeater |
| US3636453A (en) * | 1969-05-07 | 1972-01-18 | Cutler Hammer Inc | Concurrent same-frequency fm radio repeater |
| US3611139A (en) * | 1970-02-25 | 1971-10-05 | Us Navy | Orthogonal mixer f{11 {0 f{11 {0 repeater |
| US3987396A (en) * | 1975-07-17 | 1976-10-19 | Xetron Corporation | Repeater system |
-
1978
- 1978-08-28 US US05/937,295 patent/US4218772A/en not_active Expired - Lifetime
-
1979
- 1979-06-11 CA CA000329508A patent/CA1117601A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US4218772A (en) | 1980-08-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |